JP4738615B2 - Imaging apparatus, imaging method, program, and storage medium - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an imaging apparatus and an imaging method for forming an image by visible light or radiation, and relates to a one-dimensional or two-dimensional imaging apparatus and imaging method such as a facsimile, a digital copying machine, a still camera, or a radiation imaging apparatus.
[0002]
[Prior art]
Conventionally, an image sensor using a single crystal sensor represented by a CCD sensor or a MOS sensor or a PIN sensor of hydrogenated amorphous silicon (hereinafter referred to as a-Si) is one-dimensional or two-dimensional. Various imaging devices using large-sized sensors arranged are produced.
[0003]
These imaging apparatuses not only form visible light images but also develop imaging apparatuses that convert radiation images into electrical signals with the development of nuclear power development, radiological medical equipment, and nondestructive inspection.
[0004]
However, most of these S / Ns are 2 to 3 digits, and no more S / N was required. This is because there is no A / D converter suitable for digitizing high S / N output with high accuracy, and the amount of data after conversion becomes large, so it is easy to use due to memory limitations and communication limitations. This is because, as a result, the necessity for a high S / N imaging device was small.
[0005]
However, in recent years, development of a large-capacity memory and high-speed communication has been remarkable, and accordingly, there has been an increasing demand for an imaging apparatus having a high S / N of 4 to 5 digits.
[0006]
However, the S / N drop due to variations in the fixed pattern and sensitivity is unavoidable due to variations in the production process, and in order to prevent this, the fixed pattern and sensitivity variations are stored in the memory at the time of shipment from the factory. Although a method of correcting with the information of the shooting output and this memory was taken, since the data used for correction is taken before shooting with this method, the conditions under which imaging was actually performed and the data used for correction The fixed pattern and sensitivity variations that cause a decrease in S / N are slightly different under these conditions, so that the error included in the photographic output was not completely corrected.
[0007]
Therefore, in Japanese Patent Laid-Open No. 10-327317, in an imaging apparatus having an imaging means including a plurality of photoelectric conversion elements arranged one-dimensionally or two-dimensionally, the imaging output in the imaging mode is stored, and then light is incident. A method is disclosed in which the shooting output is corrected using the correction output obtained in the correction mode in which the camera is operated using the same shooting conditions as in the shooting mode. Hereinafter, such a conventional example will be described with reference to the drawings.
[0008]
FIG. 1 is an overall system block diagram of a conventional imaging apparatus. In this conventional example, a radiation imaging apparatus for medical X-ray diagnosis is configured.
[0009]
In FIG. 1, reference numeral 10 denotes an X-ray source capable of emitting X-rays 13 in the form of pulses. The AE controller 30 serving as an imaging condition control means turns on / off the X-ray pulses and the tube voltage of the tube in the X-ray source. The tube current is controlled. X-rays 13 emitted from the X-ray source 10 pass through a subject 11 which is a patient to be diagnosed and enter a phosphor 12 composed of CsI, Gd2 O2 S, etc. that converts X-rays into visible light. At this time, X-rays transmitted through the subject 11 have different amounts of transmission depending on the bone inside the subject 11, the size and shape of the built-in subject, and the presence or absence of a lesion, and include image information thereof. This X-ray 13 is converted into visible light by the phosphor 12 and enters the two-dimensional area sensor 20 serving as image pickup means as image information light 14. The two-dimensional area sensor 20 includes a plurality of photoelectric conversion elements arranged two-dimensionally and a drive circuit that drives them, and converts the image information light 14 into an electric signal including two-dimensional information and outputs the electric signal.
[0010]
The two-dimensional area sensor 20 is controlled by an AE controller 30 for accumulation time and driving speed. The output of the two-dimensional area sensor 20 is input to the gain adjustment circuit 21 and also input to the AE controller 30 as information for controlling the photographing conditions.
[0011]
The outputs of the control panel 32, temperature sensor 33 and phototimer 31 are also input to the AE controller 30 in order to control shooting conditions. In the control panel 32, conditions are input by panel operation so that a doctor or an engineer can obtain an optimal imaging output for each imaging exposure in consideration of a patient's symptom, physique, age and information to be obtained, and is converted into an electrical signal and is converted into an AE. Input to the controller 30.
[0012]
The temperature sensor 33 detects the temperature of a component whose characteristics change and the optimum operating condition changes depending on the temperature, such as the room temperature, tube temperature, and two-dimensional area sensor 20 at the time of photographing exposure, and inputs them to the AE controller 30. Is done. These detected temperatures are preferably the temperatures at the time of photographing exposure.
[0013]
The phototimer 31 is placed between the subject 11 and the two-dimensional area sensor 20, detects the amount of X-rays that pass through a reference portion (eg, alveolar portion) of the subject 11 during photographing exposure, and is input to the AE controller 30. The Since the X-ray absorption by the phototimer 31 is very small, it hardly affects the photographic exposure.
[0014]
The AE controller 30 determines the X-ray pulse width of the X-ray source 10, the accumulation time / drive speed of the two-dimensional area sensor 20, and the gain adjustment circuit 21 based on these input values immediately before photographing exposure or values during photographing exposure. The gain can be controlled automatically and controlled. With these controls, the output of the gain adjustment circuit 21 can be set to an appropriate photographing output.
[0015]
At this time, the conditions controlled and set by the AE controller 30 at the time of photographing exposure can be stored as condition values in the condition memory circuit 40 serving as condition storage means. The condition memory circuit 40 can store the conditions, and at the same time, can input the stored condition values to the AE controller 30. At this time, the AE controller 30 can control and set the X-ray source 10, the two-dimensional area sensor 20, and the gain adjustment circuit 21 based on the condition value input from the condition memory circuit 40. That is, it is possible to perform exposure again with the same control / setting as the previous exposure conditions. At this time, by making a part of the conditions and control / setting different, it is possible to make the correction exposure and to make the output of the gain adjustment circuit 21 the correction output. In other words, if the system is operated without emitting an X-ray pulse and the others are the same as in the previous imaging exposure, a correction output of the dark output of the two-dimensional area sensor 20 can be obtained.
[0016]
In FIG. 1, the inside of the broken line of the correction circuit 80 is a correction circuit, and the photographic output obtained at the time of photographic exposure can be recorded once in the frame memory 50 as the photographic output storage means via the switch 51, and the corrected output B obtained at the time of corrected exposure. The image processing output 60 stored in the frame memory 50 can be processed by the arithmetic processing circuit 60 to obtain an image information output O from which an error at the time of shooting is removed. This image information output O is transmitted to an image processing system or the like.
[0017]
Reference numeral 70 denotes a system control circuit which detects that the photographing exposure start button 71 has been pressed, and controls the X-ray source 10, the two-dimensional area sensor 20, and the gain adjustment circuit 21 via the AE controller 30 (not shown). Then, photographing exposure and correction exposure are performed, and the switch 51, the frame memory 50, and the arithmetic processing circuit 60 are controlled to operate as the correction circuit 80.
[0018]
FIG. 2 is an overall circuit diagram showing the configuration of the two-dimensional area sensor 20. In addition, the same code | symbol is attached | subjected to the part of the same function as FIG.
[0019]
2, S11 to S33 are photoelectric conversion elements, and the lower electrode side is indicated by G and the upper electrode side is indicated by D. C11 to C33 are storage capacitors, and T11 to T33 are transfer TFTs. Vs is a read power source and Vg is a refresh power source, which are connected to the G electrodes of the photoelectric conversion elements S11 to S33 via switches SWs and SWg, respectively. The switch SWs is directly connected to the refresh control circuit RF through an inverter, and is controlled so that SWg is on during the refresh period and SWs is on during the other periods.
[0020]
One pixel is composed of one photoelectric conversion element, a capacitor, and a TFT, and its signal output is connected to the detection integrated circuit IC by a signal wiring SIG. This two-dimensional area sensor divides a total of nine pixels into three blocks, simultaneously transfers the output of three pixels per block, and is sequentially converted into an output by the integrated circuit for detection through this signal wiring and output. Each pixel is arranged two-dimensionally by arranging three pixels in one block in the horizontal direction and arranging the three blocks in the vertical direction in order.
[0021]
Next, the operation of the conventional radiation imaging apparatus will be described with reference to FIGS. As described above, the photoelectric conversion element in the conventional example operates as an optical sensor that outputs a photocurrent proportional to the incident light in the photoelectric conversion mode if it is periodically refreshed. FIG. 3 is a timing chart showing the operation of the imaging apparatus.
[0022]
First, a doctor or a technician places a patient to be diagnosed, that is, the subject 11 between the X-ray source 10 and the two-dimensional area sensor 20 and poses the subject so that the part to be diagnosed can be observed. At the same time, conditions are input to the control panel 32 so that an optimal imaging output can be obtained in consideration of the patient's symptoms, physique, age, and information to be obtained in advance through an inquiry or the like. This signal is transmitted to the AE controller 30 as an electrical signal. At the same time, these conditions are stored in the condition memory circuit 40.
[0023]
In this state, when the doctor or engineer presses the photographing exposure start button 71, the photographing mode is started. First, the system control circuit 70 causes the two-dimensional area sensor 20 to perform a refresh operation. Here, the refresh operation will be described. First, Hi is applied to the control wirings g1 to g3 and s1 to s2 by the shift registers SR1 and SR2. Then, the transfer TFTs T11 to T33 and the switches M1 to M3 are turned on, and the D electrodes of the photoelectric conversion elements S11 to S33 are set to the GND potential (because the input terminal of the integration detector Amp is designed to the GND potential). ). At the same time, the refresh control circuit RF outputs Hi, the switch SWg is turned on, and the G electrodes of the photoelectric conversion elements S11 to S33 are set to a positive potential by the refresh power supply Vg. Then, the photoelectric conversion elements S11 to S33 enter a refresh mode and are refreshed. Next, the refresh control circuit RF outputs Lo, the switch SWs is turned on, and the G electrodes of the photoelectric conversion elements S11 to S33 are set to a negative potential by the reading power source Vs. Then, the photoelectric conversion elements S11 to S33 enter the photoelectric conversion mode, and the capacitors C11 to C33 are initialized at the same time. In this state, Lo is applied to the control wirings g1 to g3 and s1 to s2 by the shift registers SR1 and SR2. Then, the transfer TFTs T11 to T33 and the switches M1 to M3 are turned off, and the D electrodes of the photoelectric conversion elements S11 to S33 are opened in DC, but the potential is held by the capacitors C11 to C13. However, since no X-rays are incident at this time, no light is incident on the photoelectric conversion elements S11 to S33 and no photocurrent flows. This completes the refresh operation.
[0024]
At this time, the temperature sensor 33 detects the temperature of a component whose characteristics change according to the temperature and changes the optimum operating condition, such as the room temperature, the tube temperature, and the two-dimensional area sensor 20 at the time of photographing exposure, and the AE controller 30. These detected temperatures are exactly the temperatures immediately before exposure. At the same time, these temperatures are stored as conditions in the condition memory circuit 40.
[0025]
Here, the AE controller determines initial conditions at the time of photographing exposure based on information from the control panel 32 and information from the temperature sensor 33. At the same time, these initial conditions are stored in the condition memory circuit 40. The contents of the initial conditions are the voltage, current and maximum pulse width of the tube of the X-ray source 10 and the driving speed of the two-dimensional area sensor 20. For example, if the chest is set on the control panel 32, the voltage of the tube of the X-ray source 10 is high, and the condition is set low for the abdomen. If the patient is instructed by the control panel 32 to be a child or a pregnant woman, the termination condition by the phototimer 31 is set short and the maximum pulse width is also set short. When the temperature of the two-dimensional area sensor 20 is high, the dark current of the photoelectric conversion element is high, but the TFT has high capability, so that the driving speed is increased to suppress dark current accumulation and to prevent the S / N from being lowered, or vice versa. When the temperature is low, the capability of the TFT is low, but the dark current of the photoelectric conversion element is also low, so the driving speed is lowered to suppress image distortion due to a decrease in TFT charge transfer.
[0026]
Under this initial condition, X-rays are emitted, pass through the subject 11, enter the phosphor 12, and are converted into light, and the light enters each of the photoelectric conversion elements S11 to S33. At the same time, the light enters the phototimer 31 placed between the subject 11 and the two-dimensional area sensor 20. These lights contain information on the internal structure of the human body. The output of the phototimer 31 is input to the AE controller 30 at any time, and when the integration of this value exceeds a certain value determined by the initial conditions, the AE controller 30 stops the X-ray. Thereby, an optimum exposure amount can be obtained in the photographic exposure. If the maximum pulse width determined by the initial conditions is reached, the AE controller 30 stops the X-ray regardless of the photosensor 31. At this time, the condition memory circuit 40 stores the actually emitted pulse width as the exposure time.
[0027]
A certain amount of the photocurrent caused by this light is accumulated in each of the capacitors C11 to C33 as electric charges and is retained even after the end of X-ray incidence. Next, the two-dimensional area sensor 20 performs a reading operation. The shift register SR1 applies a Hi control pulse to the control wiring g1, and v1 to v3 are sequentially output through the transfer TFTs T11 to T13 and the switches M1 to M3 by applying the control pulse to the control wirings s1 to s3 of the shift register SR2. Is done. Similarly, other optical signals are output under the control of the shift registers SR1 and SR2. Thereby, the two-dimensional information of the internal structure of the human body or the like is obtained as v1 to v9.
[0028]
These outputs are input to the gain adjustment circuit 21 and also to the AE controller 30. The AE controller 30 determines gains for setting these outputs to appropriate values as needed, stores the values in the condition memory circuit 40, and instructs the gain adjustment circuit 21 at the same time. As a result, the output of the gain adjustment circuit 21 becomes an optimum photographing output for processing them later. This photographing output is once recorded in the frame memory 50 which is a photographing output storage means via the switch 51 controlled by the system control circuit 70.
[0029]
As described above, the AE controller 30 controls the X-ray source 10, the two-dimensional area sensor 20, and the gain adjustment circuit 21 in almost real time by setting and outputting the control panel 32, temperature sensor 33, phototimer 31, and two-dimensional area sensor 20. As a result, photographing output can be obtained under various conditions close to the optimum. This ends the shooting mode.
[0030]
Next, the system control circuit 70 enters the correction mode and refreshes the two-dimensional area sensor 20 again. After completion of the refresh, various conditions stored in the condition memory circuit 40 are called to the AE controller 30 at the time of photographing exposure. Except for the X-ray source 10, the operation is performed under exactly the same conditions as in the imaging mode. That is, the operation is performed based on the value stored in the condition memory circuit 40 without using the output of the temperature sensor 33 or the phototimer 31. The X-ray source 10 is not operated in the correction mode, and X-rays are not emitted. However, the two-dimensional area sensor 20 performs the reading operation after waiting for a time corresponding to the exposure time in the imaging mode without moving the X-ray source 10. The drive speed and the gain of the gain adjustment circuit 21 are operated under the same conditions as in the shooting mode. The output of the gain adjustment circuit 21 at this time is set as a correction output. That is, the X-ray source 10, the two-dimensional area sensor 20, and the gain adjustment circuit 21 can be set and controlled to values stored in the condition memory circuit 40 to obtain a correction output.
[0031]
This correction output reflects the dark current of each pixel, fixed pattern noise during transfer, the offset voltage of the amplifier and gain adjustment circuit 21 in the two-dimensional area sensor 20, and the like. Since this correction output has the same accumulation time as in the photographing mode, the influence amount due to the accumulation of current during dark is also the same. Further, since this correction output has the same driving speed, the influence amount of the fixed pattern due to the influence of the clock leak or the like is also the same. Further, since the gain is the same, the influence amount of the offset voltage is also the same. That is, since the condition memory circuit 40 performs the same operation except for the X-ray source in the imaging mode and the correction mode, not only the influence amount described above but also all the influence amounts that are undesirable for imaging other than X-ray emission and non-emission are the same. become. Therefore, the correction output includes only the same amount of undesired errors in the photographing output.
[0032]
Therefore, the shooting output stored in the frame memory 50 is A, the correction output obtained in the correction mode is B, and the arithmetic processing circuit 60 performs subtraction processing.
O = A-B
Then, it is possible to obtain a good image information output O from which an error such as a fixed pattern of the photographing output obtained in the photographing mode is removed.
[0033]
However, the above can be said that the power source of the two-dimensional area sensor is turned on, that is, the G electrodes of the photoelectric conversion elements S11 to S33 are in a stable state after a lapse of a predetermined time after being set to a negative potential by the reading power source Vs. This is the case. Therefore, after the device is turned on, the G electrodes of the photoelectric conversion elements S11 to S33 are set to a negative potential with the reading power source Vs to be in a stable state, and thereafter, a state in which a negative voltage is applied to the G electrode is maintained until the device is turned off. It was.
[0034]
However, such a two-dimensional area sensor has a drawback that its performance deteriorates when a voltage is applied to the G electrodes of the photoelectric conversion elements S11 to S33 for a long time. In order to improve this, a sleep state in which voltage application is stopped is applied to the G electrodes of the photoelectric conversion elements S11 to S33 except during shooting, and voltage application is applied to the G electrodes of the photoelectric conversion elements S11 to S33 during shooting. It is necessary to use a driving method of setting the ready state to be performed.
[0035]
FIG. 4 is a timing chart showing such drive control. m indicates an imaging mode or correction mode, p indicates the sleep state or the ready state, x indicates X-ray exposure, and d indicates a change in dark current. After changing from the sleep state (voltage application to the G electrodes of the photoelectric conversion elements S11 to S33 is stopped) to the ready state (voltage application to the G electrodes of the photoelectric conversion elements S11 to S33) from the point a, a considerably long predetermined time ( After the elapse of about 10 seconds, the shooting mode is set from point b to point c, and the correction mode is set from point d to point e.
[0036]
[Problems to be solved by the invention]
However, in the above conventional example, there is a change in dark current caused by applying a voltage to the G electrode of the photoelectric conversion element. Dk in FIG. 4 indicates a change in dark current caused by applying a voltage to the G electrode of the photoelectric conversion element, and after the dark current becomes large at a point where the sleep state is changed to the ready state, time elapses. It shows how it decreases with time. In FIG. 4, the influence of the change in the dark current as described above is avoided by performing photographing and correction at the points b to e where the dark current is almost constant. However, it is necessary to set a large waiting time (usually about 10 seconds) in order to make the dark current almost constant after the ready state. In other words, there was a drawback that it would be a user-friendly device.
[0037]
On the other hand, in order to avoid the above disadvantages and reduce the waiting time, if the shooting mode or the correction mode is performed immediately from the point a which has been changed from the sleep state to the ready state, the correction will be performed when the dark current changes. Therefore, there is a drawback that an error is generated by the amount of the change and correction cannot be performed with high accuracy. FIG. 5 is a signal diagram for explaining an error when the waiting time is reduced as described above. When the change in dark current of dk is abrupt, the A shooting mode and the B correction mode are performed. The A shooting mode and the B correction mode correspond to A and B in FIG. 3, and the outputs from v1 to v9 of A and B are taken into consideration that the dark current changes as dk. And v1 (A) -v1 (B) ≡v1 (AB),
v1 (AB)> v2 (AB)> ...> v9 (AB)
Therefore, a correction error occurs.
[0038]
FIG. 6 illustrates such a correction error, and the size of (AB) of the outputs v1 to v9 is represented by a bar graph corresponding to S11 to S33 in FIG. As described above, when the shooting mode or the correction mode is performed immediately from the point a that is changed from the sleep state to the ready state, the intensity distribution is generated as shown in FIG. When this is viewed as an image, the upper left corner is bright and the lower right corner is dark, which has an undesirable effect on the image to be obtained. (As shown in FIG. 4, when the A shooting mode and the B correction mode are performed when the dark current of dk becomes constant, v1 (AB) to v9 (AB) in FIG. 6 become zero. (The effect of the change in the dark current is zero, and the corrected output includes only the same amount of undesired errors in the shooting output.)
[0039]
The present invention has been made to solve such a problem, and imaging capable of obtaining an imaging output with a small error even when waiting time from an actual imaging to an actual imaging is small. An object is to provide an apparatus, an imaging method, and a storage medium.
[0040]
[Means for Solving the Problems]
  The imaging apparatus of the present inventionAn imaging means including a plurality of photoelectric conversion elements arranged two-dimensionally and including a dummy photoelectric conversion element that does not detect light, a means for storing an imaging output at the time of imaging, and an imaging condition at the time of imaging Means for storing the correction output obtained by operating the imaging means using the stored imaging conditions in a state where no light is incident after the imaging, and the dummy Means for subtracting the difference between the photographing output and the correction output of the dummy photoelectric conversion element from the difference between the photographing output and the correction output of the photoelectric conversion element that is not a photoelectric conversion element of the photoelectric conversion element to obtain an image information output It is characterized by having.
  The imaging method of the present invention is an imaging method by an imaging apparatus having a plurality of photoelectric conversion elements arranged two-dimensionally and including an imaging means including a dummy photoelectric conversion element that does not detect light in a part thereof, The procedure for storing the shooting output at the time of shooting, the procedure for storing the shooting conditions at the time of shooting, and the imaging means using the stored shooting conditions in a state where no light is incident after the shooting. The imaging output of the dummy photoelectric conversion element is obtained from the difference between the procedure of storing the correction output obtained by operating the imaging output of the photoelectric conversion element that is not the dummy photoelectric conversion element and the correction output. And a procedure of subtracting the difference between the correction output and the image information output.
[0057]
The program of the present invention is a program for causing a computer to execute the procedure of the above imaging method.
[0058]
The storage medium of the present invention is a computer-readable storage medium storing a program for causing a computer to execute the procedure of the imaging method.
[0059]
[Action]
  In the present invention,It has a plurality of photoelectric conversion elements arranged two-dimensionally, and includes an imaging means including a dummy photoelectric conversion element that does not detect light in part of the photoelectric conversion elementsWith imaging device,First, take a picture, get the picture output, store this picture output and the shooting conditions,After the shooting, the correction output obtained by operating the imaging means using the stored shooting conditions in a state where no light is incident is stored. And"DummyofDifference between photographing output and correction output of the photoelectric conversion element that is not a photoelectric conversion element "From"DummyPhotoelectricDifference between shooting output and correction output of conversion element "pullAs a result, it is possible to obtain a photographic output with less error and to obtain high S / N image information.
[0061]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
First, a first embodiment of the present invention will be described in detail based on the drawings. FIG. 7 is an overall system block diagram of the imaging apparatus according to the first embodiment of the present invention. In addition, the same code | symbol is attached | subjected to the part of the same function as FIG. In this embodiment, a radiation imaging apparatus for the purpose of medical X-ray diagnosis is configured.
[0062]
In FIG. 7, reference numeral 10 denotes an X-ray source capable of emitting X-rays 13 in the form of pulses. The AE controller 30 serving as an imaging condition control means turns on / off the X-ray pulses and the tube voltage of the tube in the X-ray source. The tube current is controlled. X-rays 13 emitted from the X-ray source 10 pass through a subject 11 which is a patient to be diagnosed and enter a phosphor 12 composed of CsI, Gd2 O2 S, etc. that converts X-rays into visible light. At this time, X-rays transmitted through the subject 11 have different amounts of transmission depending on the bone inside the subject 11, the size and shape of the built-in subject, and the presence or absence of a lesion, and include image information thereof. This X-ray 13 is converted into visible light by the phosphor 12 and enters the two-dimensional area sensor 20 serving as image pickup means as image information light 14. The two-dimensional area sensor 20 includes a plurality of photoelectric conversion elements arranged two-dimensionally and a drive circuit that drives them, and converts the image information light 14 into an electric signal including two-dimensional information and outputs the electric signal.
[0063]
The two-dimensional area sensor 20 is controlled by an AE controller 30 for accumulation time and driving speed. The output of the two-dimensional area sensor 20 is input to the gain adjustment circuit 21 and also input to the AE controller 30 as information for controlling the photographing conditions.
[0064]
The outputs of the control panel 32, temperature sensor 33 and phototimer 31 are also input to the AE controller 30 in order to control shooting conditions. In the control panel 32, conditions are input by panel operation so that a doctor or an engineer can obtain an optimal imaging output for each imaging exposure in consideration of a patient's symptom, physique, age and information to be obtained, and is converted into an electrical signal and is converted into an AE Input to the controller 30.
[0065]
The temperature sensor 33 detects the temperature of a component whose characteristics change and the optimum operating condition changes depending on the temperature, such as the room temperature, tube temperature, and two-dimensional area sensor 20 at the time of photographing exposure, and inputs them to the AE controller 30. Is done. These detected temperatures are preferably the temperatures at the time of photographing exposure.
[0066]
The phototimer 31 is placed between the subject 11 and the two-dimensional area sensor 20, detects the amount of X-rays that pass through a reference portion (eg, alveolar portion) of the subject 11 during photographing exposure, and is input to the AE controller 30. The Since the X-ray absorption by the phototimer 31 is very small, it hardly affects the photographic exposure.
[0067]
The AE controller 30 determines the X-ray pulse width of the X-ray source 10, the accumulation time / drive speed of the two-dimensional area sensor 20, and the gain adjustment circuit 21 based on these input values immediately before photographing exposure or values during photographing exposure. The gain can be controlled automatically and controlled. With these controls, the output of the gain adjustment circuit 21 can be set to an appropriate photographing output.
[0068]
At this time, the conditions controlled and set by the AE controller 30 at the time of photographing exposure can be stored as condition values in the condition memory circuit 40 serving as condition storage means. The condition memory circuit 40 can store the conditions, and at the same time, can input the stored condition values to the AE controller 30. At this time, the AE controller 30 can control and set the X-ray source 10, the two-dimensional area sensor 20, and the gain adjustment circuit 21 based on the condition value input from the condition memory circuit 40. That is, it is possible to perform exposure again with the same control / setting as the previous exposure conditions. At this time, by making a part of the conditions and control / setting different, it is possible to make the correction exposure and to make the output of the gain adjustment circuit 21 the correction output. In other words, if the system is operated without emitting an X-ray pulse and the others are the same as in the previous imaging exposure, a correction output of the dark output of the two-dimensional area sensor 20 can be obtained.
[0069]
In FIG. 7, reference numeral 80 denotes a correction circuit, and a shooting output obtained at the time of shooting exposure can be recorded once in the frame memory 50 as shooting output storage means via the switch 56, and a correction output obtained at the time of correction exposure via the switch 56. It can be recorded once in the frame memory 57 which is a correction output storage means, and is processed by the arithmetic processing circuit 60 using the shooting output A stored in the frame memory 50 and the correction output B stored in the frame memory 57 to eliminate errors during shooting. The image information output O can be obtained. This image information output O is transmitted to an image processing system or the like.
[0070]
Reference numeral 70 denotes a system control circuit which detects that the photographing exposure start button 71 has been pressed, and controls the X-ray source 10, the two-dimensional area sensor 20, and the gain adjustment circuit 21 via the AE controller 30 (not shown). Then, photographing exposure and correction exposure are performed, and the switch 51, the frame memory 50, and the arithmetic processing circuit 60 are controlled to operate as the correction circuit 80.
[0071]
That is, the configuration shown in FIG. 7 includes an imaging unit 20 including a plurality of photoelectric conversion elements arranged two-dimensionally, an image information incident unit 10 capable of controlling the incidence of image information light on the photoelectric conversion elements, and imaging conditions. In an imaging apparatus having a photographing condition control means 30 capable of automatic control and setting control, and a condition storage means 40 for storing conditions automatically controlled by the photographing condition control means, first, a desired photographing output is automatically controlled. The image information incident means 31 causes the image information light to enter the image pickup means 20 while operating the image pickup condition control means 30 so that the image pickup output storage means 50 stores the image pickup output at this time. The setting value selected by the condition control means 30 is stored in the condition storage means 40, and then the photographing condition control means is set according to the setting value stored in the condition storage means 40. 30, the output at this time is used as a correction output, the correction output at this time is stored in the correction output storage means 57, and the photographing output stored in the photographing output storage means 50 and the correction output storage means 57. The image pickup apparatus and the image pickup method are characterized in that the output is processed by the arithmetic processing circuit 60 using the correction output stored in FIG.
[0072]
FIG. 2 is an overall circuit diagram showing the configuration of the two-dimensional area sensor 20. 2, S11 to S33 are photoelectric conversion elements, and the lower electrode side is indicated by G and the upper electrode side is indicated by D. C11 to C33 are storage capacitors, and T11 to T33 are transfer TFTs. Vs is a read power source and Vg is a refresh power source, which are connected to the G electrodes of the photoelectric conversion elements S11 to S33 via switches SWs and SWg, respectively. The switch SWs is directly connected to the refresh control circuit RF through an inverter, and is controlled so that SWg is on during the refresh period and SWs is on during the other periods. One pixel is composed of one photoelectric conversion element, a capacitor, and a TFT, and its signal output is connected to the detection integrated circuit IC by a signal wiring SIG. The two-dimensional area sensor of this embodiment divides a total of nine pixels into three blocks and simultaneously transfers the output of three pixels per block, and is sequentially converted into an output by the integrated circuit for detection through this signal wiring and output. Each pixel is arranged two-dimensionally by arranging three pixels in one block in the horizontal direction and arranging the three blocks in the vertical direction in order.
[0073]
S11 is a photoelectric conversion element, T11 is a TFT, C11 is a capacitor, and SIG is a signal wiring. In the present embodiment, the capacitor C11 and the photoelectric conversion element S11 are not particularly separated from each other, and the capacitor C11 is formed by increasing the area of the electrode of the photoelectric conversion element S11. This is possible because the photoelectric conversion element of this embodiment and the capacitor have the same layer configuration, and is also a feature of this embodiment. A passivation silicon nitride film SiN8 and a phosphor 12 such as CsI, Gd2 O2 S are formed on the upper part of the pixel. When X-rays 13 including image information are incident from above, the phosphor 12 converts the light into image information light 14, and this light is incident on the photoelectric conversion element.
[0074]
The photoelectric conversion element is provided with a dummy photoelectric conversion element in which a light receiving surface is masked with a light shielding film or a light shielding plate so that light does not enter a part thereof. In the first embodiment, S11, S21, and S31 at the left end in FIGS. 2 and 8 are dummy photoelectric conversion element portions.
[0075]
Next, the operation of the radiation imaging apparatus according to the present embodiment will be described with reference to FIGS. 7, 2, and 3. As described above, the photoelectric conversion element in this embodiment operates as an optical sensor that outputs a photocurrent proportional to incident light in the photoelectric conversion mode if it is periodically refreshed. FIG. 3 is a timing chart showing the operation of the imaging apparatus.
[0076]
First, a doctor or a technician places a patient to be diagnosed, that is, the subject 11 between the X-ray source 10 and the two-dimensional area sensor 20 and poses the subject so that the part to be diagnosed can be observed. At the same time, conditions are input to the control panel 32 so that an optimal imaging output can be obtained in consideration of the patient's symptoms, physique, age, and information to be obtained in advance through an inquiry or the like. This signal is transmitted to the AE controller 30 as an electrical signal. At the same time, these conditions are stored in the condition memory circuit 40.
[0077]
In this state, when the doctor or engineer presses the photographing exposure start button 71, the photographing mode is started.
[0078]
In the ready state at point a in FIG. 5, that is, the power source of the two-dimensional area sensor is turned on, that is, the G electrodes of the photoelectric conversion elements S11 to S33 are set to a negative potential by the reading power source Vs. Next, the system control circuit 70 causes the two-dimensional area sensor 20 to perform a refresh operation. Here, the refresh operation will be described. First, Hi is applied to the control wirings g1 to g3 and s1 to s2 by the shift registers SR1 and SR2. Then, the transfer TFTs T11 to T33 and the switches M1 to M3 are turned on, and the D electrodes of the photoelectric conversion elements S11 to S33 are set to the GND potential (because the input terminal of the integration detector Amp is designed to the GND potential). ). At the same time, the refresh control circuit RF outputs Hi, the switch SWg is turned on, and the G electrodes of the photoelectric conversion elements S11 to S33 are set to a positive potential by the refresh power supply Vg. Then, the photoelectric conversion elements S11 to S33 enter a refresh mode and are refreshed. Next, the refresh control circuit RF outputs Lo, the switch SWs is turned on, and the G electrodes of the photoelectric conversion elements S11 to S33 are set to a negative potential by the reading power source Vs. Then, the photoelectric conversion elements S11 to S33 enter the photoelectric conversion mode, and the capacitors C11 to C33 are initialized at the same time. In this state, Lo is applied to the control wirings g1 to g3 and s1 to s2 by the shift registers SR1 and SR2. Then, the transfer TFTs T11 to T33 and the switches M1 to M3 are turned off, and the D electrodes of the photoelectric conversion elements S11 to S33 are opened in DC, but the potential is held by the capacitors C11 to C13. However, since no X-rays are incident at this time, no light is incident on the photoelectric conversion elements S11 to S33 and no photocurrent flows. This completes the refresh operation.
[0079]
At this time, the temperature sensor 33 detects the temperature of a component whose characteristics change according to the temperature and changes the optimum operating condition, such as the room temperature, the tube temperature, and the two-dimensional area sensor 20 at the time of photographing exposure, and the AE controller 30. These detected temperatures are exactly the temperatures immediately before exposure. At the same time, these temperatures are stored as conditions in the condition memory circuit 40.
[0080]
Here, the AE controller determines initial conditions at the time of photographing exposure based on information from the control panel 32 and information from the temperature sensor 33. At the same time, these initial conditions are stored in the condition memory circuit 40. The contents of the initial conditions are the voltage, current and maximum pulse width of the tube of the X-ray source 10 and the driving speed of the two-dimensional area sensor 20. For example, if the chest is set on the control panel 32, the voltage of the tube of the X-ray source 10 is high, and the condition is set low for the abdomen. If the patient is instructed by the control panel 32 to be a child or a pregnant woman, the termination condition by the phototimer 31 is set short and the maximum pulse width is also set short. When the temperature of the two-dimensional area sensor 20 is high, the dark current of the photoelectric conversion element is high, but the TFT has high capability, so that the driving speed is increased to suppress dark current accumulation and to prevent the S / N from being lowered, or vice versa. When the temperature is low, the capability of the TFT is low, but the dark current of the photoelectric conversion element is also low, so the driving speed is lowered to suppress image distortion due to a decrease in TFT charge transfer.
[0081]
Under this initial condition, X-rays are emitted, pass through the subject 11, enter the phosphor 12, and are converted into light, and the light enters each of the photoelectric conversion elements S11 to S33. At the same time, the light enters the phototimer 31 placed between the subject 11 and the two-dimensional area sensor 20. These lights contain information on the internal structure of the human body. The output of the phototimer 31 is input to the AE controller 30 at any time, and when the integration of this value exceeds a certain value determined by the initial conditions, the AE controller 30 stops the X-ray. Thereby, an optimum exposure amount can be obtained in the photographic exposure. If the maximum pulse width determined by the initial conditions is reached, the AE controller 30 stops the X-ray regardless of the photosensor 31. At this time, the condition memory circuit 40 stores the actually emitted pulse width as the exposure time.
[0082]
A certain amount of the photocurrent caused by this light is accumulated in each of the capacitors C11 to C33 as electric charges and is retained even after the end of X-ray incidence. Next, the two-dimensional area sensor 20 performs a reading operation. The shift register SR1 applies a Hi control pulse to the control wiring g1, and v1 to v3 are sequentially output through the transfer TFTs T11 to T13 and the switches M1 to M3 by applying the control pulse to the control wirings s1 to s3 of the shift register SR2. Is done. Similarly, other optical signals are output under the control of the shift registers SR1 and SR2. Thereby, the two-dimensional information of the internal structure of the human body or the like is obtained as v1 to v9.
[0083]
These outputs are input to the gain adjustment circuit 21 and also to the AE controller 30. The AE controller 30 determines gains for setting these outputs to appropriate values as needed, stores the values in the condition memory circuit 40, and instructs the gain adjustment circuit 21 at the same time. As a result, the output of the gain adjustment circuit 21 becomes an optimum photographing output for processing them later. This photographing output is once recorded in the frame memory 50 as photographing output storing means via the switch 56 controlled by the system control circuit 70.
[0084]
As described above, the AE controller 30 controls the X-ray source 10, the two-dimensional area sensor 20, and the gain adjustment circuit 21 in almost real time by setting and outputting the control panel 32, temperature sensor 33, phototimer 31, and two-dimensional area sensor 20. As a result, photographing output can be obtained under various conditions close to the optimum. This ends the shooting mode.
[0085]
Next, the system control circuit 70 enters the correction mode and refreshes the two-dimensional area sensor 20 again. After completion of the refresh, various conditions stored in the condition memory circuit 40 are called to the AE controller 30 at the time of photographing exposure. Except for the X-ray source 10, the operation is performed under exactly the same conditions as in the imaging mode. That is, the operation is performed based on the value stored in the condition memory circuit 40 without using the output of the temperature sensor 33 or the phototimer 31. The X-ray source 10 is not operated in the correction mode, and X-rays are not emitted. However, the two-dimensional area sensor 20 performs the reading operation after waiting for a time corresponding to the exposure time in the imaging mode without moving the X-ray source 10. The drive speed and the gain of the gain adjustment circuit 21 are operated under the same conditions as in the shooting mode. The output of the gain adjustment circuit 21 at this time is set as a correction output. That is, the X-ray source 10, the two-dimensional area sensor 20, and the gain adjustment circuit 21 can be set and controlled to values stored in the condition memory circuit 40 to obtain a correction output. This correction output is recorded in a frame memory 57 as a correction output storage means via a switch 56 controlled by the system control circuit 70.
[0086]
This correction output reflects the dark current of each pixel, fixed pattern noise during transfer, the offset voltage of the amplifier and gain adjustment circuit 21 in the two-dimensional area sensor 20, and the like. Since the correction output has the same driving speed, the influence amount of the fixed pattern due to the influence of the clock leak or the like is also the same. Further, since the gain is the same, the influence amount of the offset voltage is also the same. However, this correction output has the same accumulation time as in the shooting mode, but immediately after it becomes ready, so the amount of influence due to the accumulation of current during dark is different. In other words, since the condition memory circuit 40 performs the same operation except for the X-ray source in the imaging mode and the correction mode, it is not preferable for imaging other than X-ray emission and non-emission except for the current during dark of each pixel described above. The amount will be the same.
[0087]
Therefore, the influence due to the accumulation of current during dark is corrected as follows. FIG. 8 is a diagram showing a method of correcting the output value of the photoelectric conversion element arranged as shown in FIG.
[0088]
The imaging output A is v1 (A) to v9 (A), and the correction output B is a frame which is a correction output storage means. The two-dimensional information indicating the output at the time of shooting recorded in the frame memory 50 which is the imaging output storage means. Two-dimensional information indicating the output at the time of correction recorded in the memory 57 is v1 (B) to v9 (B).
[0089]
8 is a value obtained by subtraction processing (shooting output A−correction output B) by the arithmetic processing circuit 60 in FIG. Note that v1 (A) -v1 (B) is simplified as v1 (A-B) or the like. Here, if S11, S21, and S31 at the left end in FIG. 8 are dummy photoelectric conversion element portions, v1 (AB), v4 (AB), and v7 (AB) are imaging outputs of the dummy photoelectric conversion element portions. And the correction output, which represents the effect of current accumulation in the dark. Moreover, v2 (AB), v3 (AB), v5 (AB), v6 (AB), v8 (AB), and v9 (AB) are corrected as before. It is.
[0090]
Therefore, the correction 2-1 in FIG. 8 is the result of correction as before, v2 (AB), v3 (AB), v5 (AB), v6 (AB), v8 (AB). ), A value obtained by subtracting the difference between the imaging output and the correction output of the dummy photoelectric conversion element portion at the left end portion of the corresponding row from v9 (AB). That is, v1 (AB) is subtracted from v2 (AB) and v3 (AB), v4 (AB) is subtracted from v5 (AB) and v6 (AB), and v8. (A-B), v9 (A-B) is obtained by subtracting v7 (A-B).
[0091]
This is corrected for v2 (A-B) and v3 (A-B) on the assumption that the effect of current accumulation during dark is affected by the amount of v1 (A-B) at the left end. Is. Similarly, it is assumed that v5 (AB) and v6 (AB) are affected by the accumulation of current during darkness by the amount of v4 (AB) at the left end, and v8 (AB) and v9 (AB) are corrected on the assumption that the influence of current accumulation during dark is affected by the amount of v7 (AB) at the left end.
[0092]
In this way, it is possible to obtain a good image information output in which the influence of the fixed pattern or the like of the photographing output obtained in the photographing mode and the influence due to the accumulation of current in the dark are removed. In FIG. 6, when s12, s22, and s32 are dummy photoelectric conversion elements, the left s11, s21, and s31 portions and the right s13, s23, and s33 portions are not continuous. A dead area is created, and vertical lines appear in the image area. However, in this embodiment, the position of the dummy photoelectric conversion element is provided at the end of the two-dimensional arrangement, so light is actually detected. The possible photoelectric conversion elements can be continuously arranged, and the dummy element part can be eliminated in the two-dimensional arrangement, so that a good image without insensitive parts in the image is obtained.
[0093]
(Second Embodiment)
Next, a second embodiment of the present invention will be described. A major difference of the second embodiment compared to the first embodiment is the correction method of FIG. The other parts are almost the same as those of the first embodiment, and only different parts will be described with reference to FIG.
[0094]
FIG. 9 is a diagram showing an output value of the photoelectric conversion elements arranged as shown in FIG. 2 and a correction method according to the second embodiment. The correction is performed by subtracting the arithmetic processing circuit 60 using A as the shooting output stored in the frame memory 50 and B as the correction output stored in the frame memory 57.
[0095]
Here, if S13, S23, and S33 at the right end in FIG. 9 are dummy photoelectric conversion element portions, v3 (A−B), v6 (A−B), and v9 (A−B) in the correction 1 diagram of FIG. This is the difference between the photographing output and the correction output of the dummy photoelectric conversion element portion, and this represents the influence of current accumulation during darkness. The difference from FIG. 9 showing the first embodiment is that the dummy light conversion element is the right end instead of the left end. And v1 (AB), v2 (AB), v4 (AB), v5 (AB), v7 (AB), and v8 (AB) are the results corrected as before. is there. Since the correction 1 is the same as that of the first embodiment, the description thereof is omitted.
[0096]
The correction 2-2 in FIG. 9 is the result of correction as before, v1 (AB), v2 (AB), v4 (AB), v5 (AB), v7 (AB). , V8 (A−B) is a value corrected by subtracting the difference between the imaging output and the correction output of the dummy photoelectric conversion element portion at the right end of the corresponding row. That is, v3 (AB) is subtracted from v1 (AB) and v2 (AB), v6 (AB) is subtracted from v4 (AB) and v5 (AB), and v7 V9 (AB) is subtracted from (AB) and v8 (AB).
[0097]
This is performed by correcting v1 (A-B) and v2 (A-B) on the assumption that the influence of current accumulation during dark is affected by the amount of v3 (A-B) at the right end. Is. Similarly, it is assumed that v4 (AB) and v5 (AB) are affected by the accumulation of current during darkness by the amount of v6 (AB) at the right end, and v7 (AB) and v8 (AB) are corrected on the assumption that the influence of the accumulation of current during dark is affected by the amount of v9 (AB) at the right end.
[0098]
In this way, it is possible to obtain a good image information output in which the influence of the fixed pattern or the like of the photographing output obtained in the photographing mode and the influence due to the accumulation of current in the dark are removed.
[0099]
(Third embodiment)
Next, a third embodiment of the present invention will be described. The major difference of the third embodiment compared to the first and second embodiments is the correction method of FIGS. The other parts are almost the same as those of the first and second embodiments, and only different parts will be described with reference to FIG.
[0100]
FIG. 10 is a diagram illustrating an output value of the photoelectric conversion elements arranged as shown in FIG. 2 and a correction method according to the third embodiment. In the correction, the shooting output stored in the frame memory 50 is set as A, the correction output stored in the frame memory 57 is set as B, and the calculation processing circuit 60 performs a subtraction process and the following calculation.
[0101]
Here, if S11, S21, and S31 at the left end portion and S13, S23, and S33 at the right end portion in FIG. 10 are dummy photoelectric conversion element portions, v1 (AB) and v4 (AB) in the correction 1 diagram of FIG. ), V7 (A-B), v3 (A-B), v6 (A-B), and v9 (A-B) are the differences between the imaging output and the correction output of the dummy photoelectric conversion element, which are dark. Represents the effect of current accumulation. The difference from FIGS. 8 and 9 showing the first and second embodiments 1 and 2 is that the dummy light conversion elements are left and right ends instead of the left end and the right end. And v2 (AB), v5 (AB), and v8 (AB) are the results corrected as usual. Since the correction 1 is the same as in the first and second embodiments, the description thereof is omitted.
[0102]
The correction 2-3 in FIG. 10 is the result of correction in the conventional manner, and the dummy photoelectric conversion element portions at the left and right ends of the corresponding row from v2 (AB), v5 (AB), and v8 (AB). This is a value obtained by subtracting a value obtained by averaging the difference between the photographing output and the correction output. That is, (v1 (A−B) + v3 (A−B)) / 2 is subtracted from v2 (A−B), and (v4 (A−B) + v6 (A−B)) from v5 (A−B). / 2 is subtracted and (v7 (A−B) + v9 (A−B)) / 2 is subtracted from v8 (A−B).
[0103]
This is because v2 (A-B) is affected by the accumulation of current during darkness by an amount intermediate between v1 (A-B) and v3 (A-B) at the left and right ends. Correction is performed. Similarly, v5 (AB) is affected by the accumulation of current during darkness by an amount intermediate between v4 (AB) and v6 (AB) at the left and right ends. And v8 (AB) is affected by the accumulation of current during darkness by an amount intermediate between v7 (AB) and v9 (AB) at the left and right ends. Make corrections.
[0104]
In this way, it is possible to obtain a good image information output in which the influence of the fixed pattern or the like of the photographing output obtained in the photographing mode and the influence due to the accumulation of current in the dark are removed.
[0105]
In the third embodiment, since the description is made with a 3 × 3 photoelectric conversion element, correction of v2 (AB), v5 (AB), and v8 (AB) is performed on each of the left and right dummy. The average value of correction 1 of the part is used, but in the m × n photoelectric conversion element, the change due to the accumulation of current during dark of the unmasked photoelectric conversion element between the left and right dummy parts changes linearly. However, the correction 1 values of the left and right dummy portions may be linearly interpolated and correction may be performed according to the position of each photoelectric conversion element.
[0106]
Even if it is an m × n photoelectric conversion element, the average value of correction 1 of the left and right dummy portions may be used.
[0107]
(Fourth embodiment)
In the third embodiment, correction is performed, and in the case of an m × n photoelectric conversion element, the change due to the accumulation of current during dark of the unmasked photoelectric conversion element between the left and right dummy parts is linearly changed. The value of correction 1 of the left and right dummy portions is linearly interpolated and correction is performed according to the position of each photoelectric conversion element, but the dark current of unmasked photoelectric conversion elements between the left and right dummy portions If the change due to the accumulation changes according to a function, it may be performed by function interpolation using the value of correction 1 of the left and right or left end or right end dummy part.
[0108]
In the two-dimensional area sensor of the present embodiment, nine pixels are arranged two-dimensionally in 3 × 3, and three pixels are simultaneously divided and transferred and output three times. However, the present invention is not limited to this. For example, 5 × 5 per 1 mm vertically and horizontally If 2000 × 2000 pixels are arranged two-dimensionally, a two-dimensional area sensor of 40 cm × 40 cm can be obtained, and a radiation imaging apparatus for medical X-ray diagnosis can be configured. Then, unlike film, the output can be instantaneously displayed on a CRT, and further, the output can be converted to digital and converted into an output suitable for the purpose by computer processing. It can also be stored on a magneto-optical disk, and past images can be retrieved instantly. It is also possible to obtain a clear image with weak X-rays that have better sensitivity than films and have little effect on the human body.
[0109]
In this embodiment, the dummy photoelectric conversion elements are used as the left and right end portions of the reading line start point and end point. However, for example, the reading start line and the last line, that is, the upper and lower ends may be corrected as dummy photoelectric conversion elements. Further, it may be corrected as four corners of the two-dimensional arrangement, both end portions of the upper or lower end portions, and one corner of the two-dimensional arrangement.
[0110]
(Fifth embodiment)
In the fifth embodiment, the time interval Δt between the shooting mode and the correction mode is measured in the second embodiment as compared to the first embodiment. Hereinafter, the difference will be mainly described based on the first embodiment. Since this time interval changes depending on the X-ray irradiation time setting or the like, measurement is performed every time.
[0111]
This correction output reflects the dark current of each pixel, fixed pattern noise during transfer, the offset voltage of the amplifier and gain adjustment circuit 21 in the two-dimensional area sensor 20, and the like. Since the correction output has the same driving speed, the influence amount of the fixed pattern due to the influence of the clock leak or the like is also the same. Further, since the gain is the same, the influence amount of the offset voltage is also the same. However, this correction output has the same accumulation time as in the shooting mode, but immediately after it becomes ready, so the amount of influence due to the accumulation of current during dark is different. In other words, since the condition memory circuit 40 performs the same operation except for the X-ray source in the imaging mode and the correction mode, it is not preferable for imaging other than X-ray emission and non-emission except for the current during dark of each pixel described above. The amount will be the same.
[0112]
Therefore, the influence due to the accumulation of current during dark is corrected as follows. FIG. 11 is a diagram illustrating a timing indicating drive control and a correction method. This is the value of the imaging output when it is assumed that there is no X-ray irradiation from the correction outputs v1 (B) to v9 (B).₀1 (A) -v₀9 (A) is estimated, and the photographing output is corrected.
[0113]
In FIG. 11, it is assumed that the change in dark current obtained in advance is v = f (t). v is the dark current and t is the time from ready. Here, only v1 will be described for ease of explanation, but v2 to v9 are similarly calculated.
[0114]
(1) Read out the correction output v1 (B) from the frame memory 57.
(2) Since v = f (t) and v1 (B) are known, t1≡f^-1(V1 (B))
(3) Measure the time interval Δt between the shooting mode and the correction mode as described above.
(4) v in shooting mode₀The time from 1 (A) ready is t1−Δt.
(5) When v = f (t) and t1−Δt are known, it is assumed that there is no X-ray irradiation.
Shooting output v₀1 (A) (= correction value) is calculated as follows.
v₀1 (A) = f (t1−Δt)
(6) The photographing output v1 (A) from the frame memory 50 is corrected as follows.
v1 (A) -v₀1 (A)
[0115]
FIG. 12 is a diagram showing calculation results of the frame memories 50 and 57 and the calculation processing circuit 60 when correction is performed according to the correction method described above.
[0116]
In FIG. 12, “shooting output A” is the two-dimensional information v1 (A) to v9 (A) indicating the output at the time of shooting recorded in the frame memory 50 that is the shooting output storage means, and “correction output B” is The two-dimensional information indicating the output at the time of correction recorded in the frame memory 57 as the correction output storage means is v1 (B) to v9 (B). “Correction value 1” is the calculation result of (2) to (5) by the arithmetic processing circuit 60, and “Correction” is the correction result of (6) by the arithmetic processing circuit 60. As described above, in the fifth embodiment, each point is individually corrected.
[0117]
In this way, it is possible to obtain a good image information output in which the influence of the fixed pattern or the like of the photographing output obtained in the photographing mode and the influence due to the accumulation of current in the dark are removed. In the present embodiment, correction is performed using all of the correction outputs v1 (B) to v9 (B), so that the image can be accurately corrected over the entire two-dimensional arrangement, so that an accurate image is obtained.
[0118]
The graph of the change in current during darkness can be easily obtained by, for example, obtaining and plotting the outputs of v1 (B) to v9 (B) several times by changing the time from the ready. Then, based on the obtained graph, a function approximated by an exponential function may be usually obtained, or a more advanced function may be used.
[0119]
(Sixth embodiment)
Next, a sixth embodiment of the present invention will be described. The major difference of the sixth embodiment compared to the fifth embodiment is the method of setting the correction value 1 in the correction method of FIG. Others are almost the same as those of the fifth embodiment, and therefore only different parts will be described based on the correction value 2 shown in FIG.
[0120]
The figure of the correction value 2 in FIG. 13 is a calculation result by the arithmetic processing circuit 60 calculated based on the fifth embodiment. In the sixth embodiment, the correction of the same reading line is the left end correction value calculated according to (2) to (5) of the fifth embodiment.₀1 (A), v₀4 (A), v₀7 (A) is used as a correction value on each reading line, and thereafter correction is performed in the same manner as in the fifth embodiment.
[0121]
This is to correct the influence of current accumulation during darkness with the correction value at the left end of the reading line as a representative value, and it is not necessary to calculate for each point, reducing the processing time. I can do it.
[0122]
(Seventh embodiment)
Next, a third embodiment of the present invention will be described. The major difference of the seventh embodiment compared to the fifth embodiment is the method of setting the correction value 1 in the correction method of FIG. Others are almost the same as those in the fifth embodiment, and therefore only different parts will be described based on the correction value 3 shown in FIG.
[0123]
The figure of the correction value 3 in FIG. 13 is a calculation result by the arithmetic processing circuit 60 calculated based on the seventh embodiment. In the seventh embodiment, the correction of the same reading line is the right end correction value calculated according to (2) to (5) of the fifth embodiment.₀3 (A), v₀6 (A), v₀9 (A) is used as a correction value on each reading line, and thereafter correction is performed in the same manner as in the fifth embodiment.
[0124]
This is to approximately correct the influence of current accumulation in the dark using the correction value on the right of the reading line as a representative value, and it is not necessary to calculate for each point, thus shortening the processing time. I can do it.
[0125]
(Eighth embodiment)
Next, an eighth embodiment of the present invention will be described. The major difference of the eighth embodiment compared to the fifth embodiment is the method of setting the correction value 1 in the correction method of FIG. Others are almost the same as those of the fifth embodiment, and therefore only different parts will be described based on the correction value 4 shown in FIG.
[0126]
The figure of the correction value 4 in FIG. 13 is a calculation result by the arithmetic processing circuit 60 calculated based on the eighth embodiment. In the eighth embodiment, for example, the correction of the same reading line of s11, s12, and s13 is each correction value calculated according to (2) to (5) of the fifth embodiment.₀1 (A), v₀2 (A), v₀The average value of 3 (A) is used as the correction value on each reading line, and the correction of the same reading line of s21, s22, and s23 is performed according to (2) to (5) of the fifth embodiment. The value v₀4 (A), v₀5 (A), v₀The average value of 6 (A) is used as the correction value on each reading line, and the correction of the same reading line of s31, s32, and s33 is performed according to each of the corrections calculated according to (2) to (5) of the fifth embodiment. The value v₀7 (A), v₀8 (A), v₀The average value of 9 (A) is used as a correction value on each reading line, and thereafter correction is performed in the same manner as in the fifth embodiment.
[0127]
This is to approximately correct the influence of current accumulation in the dark with the average value of each correction value of the reading line as a representative value, and the influence of specific variations such as the sensitivity of the photoelectric conversion element. Therefore, it is possible to obtain good image information with little error.
[0128]
(Ninth embodiment)
Next, a ninth embodiment of the present invention will be described. In the fifth to eighth embodiments, the correction value is calculated with the change of the dark current obtained in advance as v = f (t). However, this v = f (t) is calculated in advance and the data table is calculated. It is also possible to prepare it from the table. FIG. 14 is an overall system block diagram of such an imaging apparatus according to the ninth embodiment of the present invention. Compared with the fifth to eighth embodiments, the fifth embodiment differs from the fifth embodiment in that v = f (t) in the table from the data table memory 58 connected to the arithmetic processing circuit 60 as shown in FIG. The point is that you can get the value.
[0129]
The data table to be prepared shows the value of the dark current v corresponding to the value of t, which is the time from the ready. The correction value is calculated by the same method as in the fifth embodiment. T = t1 corresponding to the correction output v = v1 (B) is read from the data table, and t1−Δt is calculated using the time interval Δt between the photographing mode and the correction mode that have been measured. From the table, v corresponding to this t = t1−Δt is read and the correction value v₀1 (A) is obtained, and v1 (A) -v is obtained as in the fifth embodiment.₀Correct as 1 (A). By using the table in this way, the time required for the calculation process can be shortened.
[0130]
(Other embodiment 1)
In the fifth and sixth embodiments described above, correction is performed using the correction value at the left or right end as the correction value on each reading line, but correction values at the midpoint position of the reading line and other positions are used. It can be used.
[0131]
In the two-dimensional area sensor of the present embodiment, nine pixels are arranged two-dimensionally in 3 × 3, and three pixels are simultaneously divided and transferred and output three times. However, the present invention is not limited to this. For example, 5 × 5 per 1 mm vertically and horizontally If 2000 × 2000 pixels are arranged two-dimensionally, a two-dimensional area sensor of 40 cm × 40 cm can be obtained, and a radiation imaging apparatus for medical X-ray diagnosis can be configured. Then, unlike film, the output can be instantaneously displayed on a CRT, and further, the output can be converted to digital and converted into an output suitable for the purpose by computer processing. It can also be stored on a magneto-optical disk, and past images can be retrieved instantly. It is also possible to obtain a clear image with weak X-rays that have better sensitivity than films and have little effect on the human body.
[0132]
In the first, second, and third embodiments described above, the dummy light conversion element that masks the light receiving surface is provided in order to prevent light from entering a part of the photoelectric conversion element. The same effect can be obtained by using a dummy conversion element in which some photoelectric conversion elements are not formed on the pattern from the beginning. Further, a capacitor equivalent to the photoelectric conversion element may be formed in a portion where it is not formed. Further, not only the photoelectric conversion element but also the TFT can be formed.
[0133]
(Other embodiment 2)
Each functional block and processing procedure shown in the various embodiments described above may be configured by hardware as described above, or may be configured by a microcomputer system including a CPU or MPU, ROM, RAM, etc. You may make it implement | achieve according to the work program stored in ROM or RAM. In addition, what is implemented by supplying a software program for realizing the function to the RAM so as to realize the function of the function block and operating the function block according to the program is also included in the scope of the present invention. include.
[0134]
In this case, the software program itself realizes the functions of the above-described embodiments, and the program itself and means for supplying the program to a computer, for example, a recording medium storing such a program are included in the present invention. Configure. As a storage medium for storing such a program, in addition to the ROM and RAM, for example, floppy disk, hard disk, optical disk, magneto-optical disk, CD-ROM, CD-I, CD-R, CD-RW, DVD, zip, A magnetic tape or a non-volatile memory card can be used.
[0135]
Further, by executing the program supplied by the computer, not only the functions of the above-described embodiments are realized, but also the OS (operating system) or other application software in which the program is running on the computer. Needless to say, such a program is included in the embodiment of the present invention even when the functions of the above-described embodiment are realized.
[0136]
Furthermore, after the supplied program is stored in the memory provided in the function expansion board of the computer or the function expansion unit connected to the computer, the CPU or the like provided in the function expansion board or function expansion unit based on the instructions of the program Needless to say, the present invention includes the case where the functions of the above-described embodiment are realized by performing part or all of the actual processing.
[0137]
【The invention's effect】
According to the present invention, it is possible to obtain a photographic output with little error even when the waiting time is short from when shooting is attempted until actual shooting is performed, and high S / N image information can be obtained.
[0138]
In addition, according to the present invention, since a dummy light conversion element whose light receiving surface is masked so that light does not enter a part of the photoelectric conversion element is used, a correction output closer to the actual can be obtained, so that a high-accuracy image can be obtained. It becomes. At this time, by forming a dummy conversion element without forming some photoelectric conversion elements from the beginning of the pattern, a device with a simpler structure and lower cost can be provided.
[0139]
In addition, according to the present invention, by providing dummy photoelectric conversion elements in the peripheral portion of the photoelectric conversion element surface, it is possible to obtain a continuous image without any chipping, so that an accurate image can be obtained.
[0140]
Further, according to the present invention, the photoelectric conversion elements arranged in two dimensions can be used effectively and maximally by correcting using the correction output value of the first or last dummy conversion element of the reading line, A small device can be provided.
[0141]
Further, according to the present invention, it is possible to perform correction with high accuracy by performing correction using the head of the reading line and the final dummy conversion element correction output value, and high S / N image information can be obtained. .
[0142]
In addition, according to the present invention, since the imaging signal is corrected using a predetermined function obtained in advance, an accurate image can be obtained.
[0143]
In addition, according to the present invention, since the imaging signal is corrected using a data table prepared in advance, it is possible to reduce the time required for calculation processing and provide a user-friendly device.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a system of a conventional imaging apparatus.
FIG. 2 is an overall circuit diagram showing a configuration of a two-dimensional area sensor.
FIG. 3 is a timing chart showing the operation of the imaging apparatus.
FIG. 4 is a timing chart showing drive control of a conventional example.
FIG. 5 is a timing chart showing drive control illustrating a problem of the conventional example.
FIG. 6 is a schematic diagram illustrating a correction error that is a problem of the conventional example.
FIG. 7 is a block diagram showing a system of the imaging apparatus according to the first embodiment of the present invention.
FIG. 8 is a schematic diagram illustrating a method for correcting the output value of the photoelectric conversion element according to the first embodiment of the present invention.
FIG. 9 is a schematic diagram illustrating a method for correcting the output value of the photoelectric conversion element according to the second embodiment of the present invention.
FIG. 10 is a schematic diagram illustrating a method for correcting an output value of a photoelectric conversion element according to a third embodiment of the present invention.
FIG. 11 is a timing chart showing a correction method according to a fifth embodiment of the present invention.
FIG. 12 is a schematic diagram showing an output value of a photoelectric conversion element and a correction method according to a fifth embodiment of the present invention.
FIG. 13 is a schematic diagram showing output values and correction methods of photoelectric conversion elements according to sixth to eighth embodiments of the present invention.
FIG. 14 is a block diagram showing a system of an imaging apparatus according to a ninth embodiment of the present invention.
[Explanation of symbols]
10 X-ray source
11 Subject
12 phosphor
13 X-ray
14 Image information light
20 Two-dimensional area sensor
21 Gain adjustment circuit
30 AE controller
31 Photo timer
32 Control panel
33 Temperature sensor
40 Conditional memory circuit
50 frame memory
51 switch
60 arithmetic processing circuit
70 System control circuit
71 Shooting exposure start button
S11 to S33 photoelectric conversion element
T11 to T33 Transfer TFT
C11 to C33 capacitors
SR1, SR2 Shift register
IC detection integrated circuit

Claims (8)

An imaging means including a plurality of photoelectric conversion elements arranged in two dimensions, and a dummy photoelectric conversion element that does not detect light in a part of the imaging means ;
Means for storing the shooting output at the time of shooting;
Means for storing photographing conditions at the time of photographing;
After the shooting, in a state where no light is incident, means for storing the corrected output obtained by operating the imaging means by using the photographing condition that has been said memory,
The dummy and the imaging output of said photoelectric conversion element is not a photoelectric conversion element from a difference between the corrected output, by subtracting the difference between the corrected output and the photographic output of the dummy photoelectric conversion element, and the image information output imaging apparatus characterized by having means for. The imaging apparatus according to claim 1 , wherein the dummy photoelectric conversion element is configured by masking so that light does not enter a part of the photoelectric conversion element. The imaging apparatus according to claim 1 , wherein the dummy photoelectric conversion element is configured by not patterning a partial region of the photoelectric conversion element. The photoelectric conversion element of the dummy, the imaging apparatus according to any one of claims 1 to 3, characterized in that arranged on the periphery of the plurality of photoelectric conversion elements arranged in the two-dimensional . The photoelectric conversion element of the dummy, according to claim 1 to 4, characterized in that the beginning and end of both or either one of the photoelectric conversion elements of each read line of the plurality of photoelectric conversion elements arranged in the two-dimensional The imaging device according to any one of the above. An imaging method by an imaging apparatus having a plurality of photoelectric conversion elements arranged two-dimensionally and having an imaging means including a dummy photoelectric conversion element that does not detect light in a part thereof,
The procedure for storing the shooting output at the time of shooting,
A procedure for storing shooting conditions at the time of shooting;
A procedure for storing a correction output obtained by operating the imaging means using the stored imaging conditions in a state where no light is incident after the imaging;
By subtracting the difference between the photographing output and the correction output of the dummy photoelectric conversion element from the difference between the photographing output and the correction output of the photoelectric conversion element that is not the dummy photoelectric conversion element, and image information output; The imaging method characterized by having the procedure to do. The program for making a computer perform the procedure of the imaging method of Claim 6 . A computer-readable storage medium storing a program for causing a computer to execute the procedure of the imaging method according to claim 6 .

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